T-Wings are mainly a ‘flow conditioning’ device, which has a small effect on clearing up the airflow to the (now for F1 2017 lower) rear wing package.

The rear wing has to work the air hard to ‘activate’ the diffuser (the part at the rear of the floor) that produces something like 60% of the overall downforce of the vehicle with very little drag consequence.

The reason they look so strange is that there is a 50mm ‘loophole’ in the regulations that allows the wing with a maximum chord length of 50mm.

The double layer t-wing will also be used to adjust the position of the center of pressure (CoP) for aero stability.

Mercedes (double T-wing), Ferrari, Williams and Haas have run T-wings since the start of the season.